Lift arm and control linkage structure for loader buckets

Abstract

A skid steer loader includes lift arms which are supported by two pairs of guide links arranged such that the bucket undergoes substantially vertical movement as it moves between lowered and raised positions. One of the pairs of guide links serves as part of a self-levelling linkage which maintains the bucket in a substantially level attitude throughout the movement of the bucket between the lowered and raised positions thereof.

We claim: 
     
       1. In a loader vehicle including a longitudinal main frame, a pair of loader arms respectively located at opposite sides of the frame, a loader bucket vertically pivotally mounted to respective forward ends of the pair of loader arms; a pair of hydraulically extensible and retractable tilt actuators respectively connected between the pair of arms and the bucket, first and second pairs of guide links respectively located with one of each pair on each side of the frame and having opposite end portions pivotally connected to the frame and to the pair of arms, and a pair of hydraulically extensible and retractable lift actuators respectively coupled between opposite sides of the frame and the pair of arms, and the first and second pairs of guide links being so dimensioned and located relative to each other and the pair of loader arms that as the latter are lifted, through operation of the lift actuators, they follow respective paths which maintain the bucket at least as far forward in any raised position as it is in a fully lowered position, the improvement comprising: said first pair of guide links each being defined by two leg portions joined to be generally L-shaped and with the respective ends of one of the two leg portions of the pair of guide links being pivotally connected to the frame; and a self-levelling linkage means, formed in part by the pair of tilt actuators, connected between the bucket and another of the two leg portions of the first pair of guide links for maintaining the bucket in substantially the same attitude throughout the movement of the lift arms. 
     
     
       2. The loader vehicle defined in claim 1 wherein the pair of lift actuators and the first pair of guide links are respectively pivotally connected to the pair of lift arms at the same location.